Data transmission systems used in the art include a single-ended signal transmission system and a differential signal transmission system. The single-ended signal transmission system uses two signal lines, i.e., a single signal line for signal transmission and a single signal line for transmitting a ground potential, to connect between a transmitting end and a receiving end. In the case of transmitting a plurality of signals in parallel, a single ground line is shared by the plurality of signals. All the electric currents representing the plurality of signals flow into the ground line at the receiving end, thereby generating, with the impedance of the ground line, a crosstalk voltage responsive to the signal levels of these signals. This crosstalk voltage is added as noise voltages to signal components at the receiving end, which may result in the signals being incorrectly received.
The differential signal transmission system uses three signal lines, i.e., a single signal line for a non-inverted signal, a single signal line for an inverted signal, and a ground line, to connect between a transmitting end and a receiving end. In the case of transmitting a plurality of signals in parallel, a single ground line is shared by the plurality of signals. Although all the electric currents representing a plurality of signals flow into the ground line at the receiving end, the voltage generated with the impedance of the ground line becomes a constant voltage, which is independent of the signal levels of these signals. This is because the electric current of each signal has a constant current amount that is the sum of the non-inverted component and the inverted component. The addition of such a constant voltage into signal components at the receiving end does not affect the reception of correct signals. Since the receiving end detects a differential component as a signal, the addition of common noise does not affect the signal detection. However, the number of signal lines used in the differential signal transmission system is approximately double the number of signal lines used in the single-ended signal transmission system. The efficiency of signal transmission per signal line is thus low, resulting in the circuit configuration being uneconomical.
[Patent Document 1] Japanese Laid-open Patent Publication No. H1188182
[Patent Document 2] Japanese Laid-open Patent Publication No. 2004104797